Envelope injection consideration of high power hybrid EER transmitter for IEEE 802.16e mobile WiMAX application

We have implemented a Hybrid Envelope Elimination and Restoration transmitter for 2.655 GHz IEEE 802.16e WiMAX applications using 90 W (P_3dB) GaN High Electron Mobility Transistor. When the tantalum capacitor is eliminated at the drain bias network of the high power amplifier (PA), bias signals at the drain and gate are seriously fluctuated due to the dasiaf2-f1psila component. To suppress the fluctuation in the H-EER transmitter, we have proposed a modified bias circuit architecture using an emitter follower. For the interlock experiment, power-added efficiency (PAE) of the transmitter has been achieved 37.04 % at an output power of 41.18 dBm with drain efficiency (DE) of 39.1 %. By using digital predistortion technique, the Relative Constellation Error (RCE) has been satisfied the specification of -30.4 dB. These results clearly show that the proposed bias circuit architecture is very effective for bias modulation techniques such as EER or ET power amplifier.